The present invention relates to selectively relieving the load on a rear axle of a vehicle, such as the rearmost axle of a trailer having at least two rear axles.
In a truck-trailer combination, the wheel base of a trailer having a single rear axle may be defined to be the distance from the pivot or king pin, where the trailer is pivoted to a vehicle, to the rear load-bearing axle of the trailer. In the case of a trailer having at least two rear load-bearing axles, the wheel base may be defined to be the distance from the king pin to the centroid of such plurality of axles. It is common for trailers to have relatively large wheel bases. When a truck-trailer combination is turned, for example, at an intersection, the rear of the trailer tends to follow a path which is inside the path followed by the vehicle during the turn rather than following the precise path of the vehicle. This is known as "off-tracking". The offset between the vehicle and trailer travel paths through a turn is greater for trailers with larger wheel bases in comparison to trailers with relatively smaller wheel bases. Also, off-tracking tends to be greater when a vehicle-trailer combination is making sharp turns in comparison to wider turns. Thus, in tight turns, such as at city intersections, the "off-tracking" trailer may be offset enough to impact street curbs or other objects at intersection corners.
It would be desirable to compensate or minimize this offset during selected vehicle operating conditions. It would particularly be useful to reduce off-tracking without requiring the vehicle to stop.